1. Field of the Invention
The present invention relates to a drill attached with a high-hard tip to a front end of a main body, a wall protector for protecting a wall surface when drilling is performed, and a method for drilling a wall.
2. Description of the Related Art
A drill for boring a hole in a wall made of concrete or other wall is attached with, as shown in FIGS. 15 and 16, a high-hard tip 2 on a front end of a main body (i.e., a shank) 1 by means of brazing or the like. This high-hard tip 2 is made of cemented carbide or the like, and is formed into a plate shape which has a width W greater than a diameter D of the main body, i.e., a diameter of a thickest portion. In FIG. 15, reference numeral 3 denotes a chuck portion which is chucked in a drill driver.
The tip 2 includes, in general, at a front end of a base portion 4, an angular cutting portion 5 protruding from the front end of the main body 1 to perform cutting. The tip 2 is attached to the main body 1 so that a vertex (i.e., the cutting point) 5a of the angular cutting portion 5 is located on an axis X of the main body 1.
On both sides of the cutting portion 5, side cutting edges 6, 7 are formed. These side cutting edges 6, 7 protrude equally diametrically outward from the main body 1 in the state where the tip 2 is attached.
The above described drill configuration is disclosed, for example, in Japanese Unexamined Patent Publication No. 2005-279853.
Such a conventional drill, as shown in FIGS. 17 to 19, cannot make in a wall A other than a straight hole B whose diameter is uniform over its full length. In FIGS. 17 to 19, for simplification, the main body 1 is illustrated in the form of a round shaft.
In the case where an anchor 7 is inserted, expanded, and fixed in the drilled hole B, and an anchor bolt 8 is screwed in the hole B, and a device or a structural member is attached to the anchor bolt 8 as shown in FIG. 18, for example, there is the problem that the fixing force of the anchor 7 in the hole B is not sufficient, thus making the attachment state of an attached object unstable.
Such problem is not limited to the so-called mechanical anchor method as shown above, but exits in the so-called chemical anchor method where an anchor is fixed by charging a hole with a synthetic resin adhesive agent. There has been the strong demand to solve this problem.